Solar mod com integration

scott markle_2

If I step off my anti active solar heating stump, my questions would be; how do you directly supplement a condensing boiler and still maintain low (high condensing) return temperatures?

If (heating) return temperatures are higher than what the collectors can produce how can we use use collector heat at all?

Trevor, I do like the idea of an idle house being heated by active solar, no DHW load = available heat. It also feels right that people with two homes do something progressive like this. My thinking is that to fully utilize the low temperatures that would be available it might make sense to dedicate a radiant slab to solar heating alone. Let this slab do what it can in-terms of surface temperature,do not supplement it with a combustion heat-source, let it cool off at night in-order that it can extract more heat the next day. To maintain a controlled room temperature and provide frost protection use panel rads and a mod-con that operates independent of this slab, on an indoor reset control.

This arrangement would leverage the heat storing capacity of the concrete,and minimize the need for additional thermal storage, simplify piping and provide an ideal low temperature heat sink for the winter solar. The panel rads with indoor reset would be sized to insure condensing operation at all operating conditions and would be very responsive to the changing contribution of the solar, as well as providing quick recovery from unoccupied mode. The only problem would be floors that would probably never feel warm, and might under some conditions (god forbid) feel cold. Basically I'm thinking that keeping the systems independent might have some advantages to direct (hydronic) integration.

Another thought; if we have a low temp heating use for the solar it might not make sense to bring our storage tank up to full (DHW) temperature unless the heating load is satisfied.

NRTDave

Solar mod com integration

Gentleman,
I have enjoyed reading many of the threads offered here. I would enjoy your feedback on my current project. I have a large solar thermal project incorporating evacuated tubes to supply DHW and space heat. My concern is not the solar.

I have installed a number of mod con systems, mostly munchkin, mostly for the three f's (friends, family and fools). I am however not in the business of installing heating systems for large elaborate homes. I feel I much better serve my clients by incorporating a good heating contractor for that purpose.

So here it is:
I want the system to operate on solar, when the heat is available. I want the response time to be appropriate, however I want to balance this with the desire to supply heat loads with heat from the solar storage tank. I then want full backup, via the modulating boiler. The system is primarily fan coil units, with infloor on one floor. I have a heating contractor who prefers TT products. He has left the control to me. I have some ideas, involving a Tekmar 263. If anyone has any info or experience, I would appreciate it greatly.

Trevor

Andrew Hagen_2

Solar Control

System 9 on page 9. Basically a temp sensor on the boiler return and a diverter valve that switches if the storage tank is warmer. It's a nice simple way to integrate solar into a mod/con system. Sorry for the poor quality pdf.

Metro Man

Careful...

Careful not to heat the solar storage tank with the boiler. Watch you plumbing! Where is this project?

Metro Man

hot_rod

crunch some numbers

to see how much of your load is actually do-able with solar. It may take a lot more panel and storage than you think. start with a simple DHW system and expand as the $$ is available.

Most of the new solar controllers will handle all the control logic for you. Three way zone valves are a simple way to switch loads and heat sources around.

The Viessmann drawings under Resources, and Green at the top of this page show some great examples.

hot rod

NRTDave

Right, the details.

Sorry, I realize that didn't offer up much in the way of detail.

Location: Telluride, CO, lat. 38, elevation: 10,000

Solar:
9 - 16 tube arrays for a total of 368 sq/ft net area of Seido 5 evacuated tubes. These are in banks of three, piped in parallel and balanced.
Storage will be two 300 gal, insulated, solar specific atmospheric tanks with two immersed heat exchangers each. Heat will be cascaded from one tank to the other, using the surplus heat function on a Resol BS solar controller (same as Stiebel Eltron). We should be able to generate 250,000 btu's a day, at 4.5 kw/m/day irradiation.

Hydronic:
A TT Presige (size to be determined by heating contractor), our thought has been to pipe the boiler as if the upper immersed heat exchanger was a second boiler. Using the Tekmar controller, we would lead with solar storage, we would then follow with the actual boiler if we couldn't supply the necessary heat. We want Outdoor reset so that we may use lower temp water, maximizing our solar storage. However we don't want to accidentally heat our storage tank with Natural Gas Either. I was hoping not to do it with a hard differential either, where you use solar tank between set temps. So that we may use lower temps at lower outside temps. Heat loads are two air handlers, snow melt (small), infloor heat, hot tub and DHW. Structure 3500 sqft, second home with lots of windows. Owners use structure 3 months a year (maybe), but very energy intensive when occupied.

My heating contractor has stopped rolling his eyes at me, however has real concerns about control and piping, as I do.
I think we are on the right path, however are we headed for a cliff.

Under three feet of Snow,
Trevor

ALH_4

Resol Control

I think your control using the "System 9" configuration will do exactly what you want to do. When the solar storage is warmer than the return temperature, the solar storage will be used to help boost the Prestige. That way you can use the tanks down to the minimum outdoor reset supply temperature minus the differential. There is potential for the supply to the heating system to be higher than the outdoor reset temperature unless you use a tekmar 356 or equivalent to "inject" the solar storage into the heating system. I think this might be a little overkill unless the solar system is very large.

Is there a way to cover the collectors when they are gone during summer months?

Metro Man

got flat plates?

Have you thougtht of using flat plate (our perference) solar collectors? Not looking at numbers right now but think a 40 sq ft collector will put out 50+ MBTU/day.... 5 - 4 x 10's to equal what you have. For the cost diff. you could add more collector area.

This system is going to cook in summer... heat dump? Power loss protection? Convert to drain-back water?

If your using tekmar then probably use the polling feature... boiler then aux heat solar. Trying to get tekmar to increase the polling time on those.

Assuming you are going with stainless steel storage tanks... lots of flexibilty there.

Good luck... you should be making turns not in front of computer!

Metro Man

NRTDave

Resol Control

Andrew,
I like the idea of allowing the heating system to set outdoor reset and only using the solar if return water is cool enough. Plus I am very familiar with the Resol line. So it would look something like this (please correct if wrong):

A set of closely spaced tees, before the boiler on the return side. If heat is available I turn on the pump through the upper immersed heat exchanger. The boiler sees the "heated" return and decides firing rate?

I like the idea of injection too, that way I don't have to pump through the boiler at all times.

As for the summer months, 1/3 of the tubes will be on a rack and will be shifted to vertical for the summer (if needed). At 10,000 ft, I have seen it snow every month. There is a call for heat almost every day (night). So we may find ourselves using up quite a bit. House also has an attached 4000 square foot addition. We are going to set second tank there to pre-feed domestic and heat hot tub.

Thanks,
Trevor

hot_rod

What is your total load?

the home alone with a high load glass front could cost you 100K or more. DHW is typically a huge load in ski homes. AND some snowmelt, yikes.

3 feet of snow will slow down those evac tubes! can you get enough tilt to keep them snow free most of the year?

Sounds like a fun job, and profitable, I trust.

I too wonder where that 250K, or more output goes all summer, especially in an empty home. Sell the output to the local carwash or laundromat

Does Telluride have a energy guzzler sin tax like Aspen?

hot rod

ALH_4

Nice

Sounds like you're on top of it. I would use injection the same way, through the boiler, particularly since the Prestige has such low head loss. Just set the tekmar curve a little higher than the Prestige. That way, the system controls are simple. The solar control will always protect you from heating the solar tank with the prestige. Using the Resol to sense the system return temp means you need to use a separate setpoint control for a heat dump, if you decide to use one.

Radman

Heat Loss?

Hey Trevor,
I chime with Hot Rod, what is the heat loss. I just ran some calcs for you in T-SOl, based upon what you already gave us and you get a space heating fraction of 3%. Not really worth it. Plus, as the Metro Man noted, that's a lot of heat to dump off in the summer. Even if you drainback, which you can with the Seidos, you will bake the header completely and be SOL after your first summer. The calcs I ran were using Boulder data, at 5000ft. If your at 10k for this house, and the load is a moderate 70K you should focus your energy (no pun intended) into the DHW only. The fan coils are killing you, and when I drop the water temp from 140 to 95, things really change for the better. You could divert solar to your low temp loads, but you don't seem to have a lot there. This would exclude the snow melt too. Just an FYI, trying to help.
I'm surprised MetroMan isn't skiing right now. I should call him.

NRTDave

Flat plates.

We don't currently distribute any flat plats, we have pretty good volume on the Seido line, therefore price. The tubes have very little losses to cold temps, wind etc. Most of our work is 7500 ft and up, so we find the losses to the environment hard when trying to do space heat using higher temp applications (FCU, convectors, etc).

We will have a heat dump, undecided if it will be buried or convector at this time (aesthetics very important). Power loss protection covered with owners genset backup.

We need tanks that we can bolt up due to doorway sizing, currently looking at NovaMAXX out of Golden.

Uncomfortable with drainback, would like to be convinced that it works well though.
Trevor

Trevor

NRTDave

Total load still being worked on.

Due to the Holiday season, I have been banned from the property (not really, but its kind of uncomfortable there). Hope to have one worked out this week. I have the past three years of gas bills though, just for fun I graphed them in excel. The property never drops below 500 therms of gas a month, even in June, July, August. Some of that is inefficient old equipment that would be replaced with new boiler and side arm.

I am only replacing the 20yr old equipment in the "main house", there is a separate wing that is serviced with an array of four WM GV boilers controlled by a Tekmar. On that side I only plan on preheating the Domestic.

We may use the seido 1 tube, you can spin them in the mainifold to modulate collection (flat collector, vs curved). They have a live-in caretaker, he has a pretty good idea for snow removal.

Telluride needs a gas guzzler tax. Some of these snowmelt systems are so large that commercial boilers are being used. I mean, I don't mind burning a little gas to be warm but, I have personally looked at systems that burn $5,000 of gas in a month, idling, (think Top Gun). Must be a better way.
Trevor

scott markle_2

active solar suspicions

It's my oft repeated opinion that active solar heating is a complicated and economically/environmentally questionable investment. Basically to have a meaningful input in the winter you will require a excess of collector area in the summer. Yes this can be overcome with a high (winter optimized) collector pitch angle. But ultimately if your goal is to do something environmentally progressive you need to look at life cycle costs.

I'm Thoroughly convinced that solar DHW is a very underutilized technology that has significant potential to reduce Co2 emissions. However it bothers me when people claim that these systems produce emission free energy. The obvious fact is that it takes energy to make these systems. From copper smelting and mining to glass and glycol. It gets pretty complicated to factor exactly what all this totals up to. Instead of trying to calculate these energy costs, from feed stocks to distribution it's easer to look at economics. How many Kw can we pull from a square meter of collector over the course of a year, how much will this equipment cost to instal and maintain and how long is likely to last? If the answer to this question is a payback period significantly less than the life of the equipment then it's worth doing. If the pay back period is half of the life span it's not as clear to me. One problem with an economic analysis is that it is made in comparison to subsidized fossil fuel, Still to omit the input of carbon based energy in the creation of solar collection systems is misleading.

The thing about active solar heating that bothers me is it's inherently inefficient utilization of a collectors energy capture potential. A collector sized (and angled) to meet summer DHW requirements will payback it's carbon debt far sooner than a bank of collectors sized for winter heating, that has been pitched to shed the summer sun.

The ironic and under recognized fact is that supplemental DHW generally (for northern latitudes) has a better payback (and environmental impact) than year round full solar capacity. Look at kw utilized per year/Sq meter.

There should be a concerted national effort to get good supplemental DHW systems on as many eligible south facing roofs as possible. I find it discouraging that (as far as I know) there are no current US manufacturers of evac. tube collectors, even though this technology was originally commercialized by U.S companies such as G.E, Corning, Owens Illinios and others.

Active solar heating has a place in homes that are specifically designed for it. But grafting this on to a conventional house with air handlers may ultimately have a very insignificant environmental impact, done wrong it may even have the potential to generate more co2 than it offsets. .

Don't forget the non-existent Chinese environmental law that makes those Sedio tubes so competitive. Sorry to be such a curmudgeon, I just think it's important to ask these questions, I guess if rich people are doing less than ideal solar projects it's good for the industry and may encourage development wether it is justifiable on it's own merits or not. You should probably have them build a pool (summer heat dump) to give a bit more legitimacy to the eco bragging rights.

NRTDave

Heat Loss

Radman,
You raise a good point, I know the fan coils really don't match up. I would love a whole bunch more of low temp loads, I have approx 1500 sqft of infloor and a little snowmelt (some steps). The problem, it's not pex and it leaks (somewhere in the snowmelt). These are currently being serviced by an ancient laars boiler. Somebody isolated from the boiler via a flat plate and rigged up a "glycol injector", which is a tank of glycol, pumped through boiler feed into that side, to make up for the slow leak. This thing scares the hell out of me. Its a disaster and I am half inclined to disable it and rely on the Fan coils (sufficient ducts, I'm assured for the load). The house currently has 320 gallons of DHW in four tanks.

I think I should go skiing, and try and absorb all you guys have given me.
Thanks,
Trevor

hot_rod

well put, Scott

by far SDHW is the best investment. every contractor that reads this needs to start looking seriously at how they can get a piece of this "green collar' work.

from what I read it looks like the production of evac tubes is still a pretty hands on labor intensive task. As such that job will probably follow the cheap labor pool. Picture from Sun & Wind Energy mag.

It amazes me that China cranked out over 20 million square meters of collector surface last year. 300 solar companies employing over 20,000 people in one area of China.

Be nice to see some of that work on this side of the pond.

hot rod

NRTDave

active solar

Scott,
You are right about active solar optimized for winter space heating being somewhat CO2 neutral in many locals. However at our elevation, we tend to use heat nearly every month of the year. The actual cost of the project when broken down, will be approx half solar, and half high efficiency conventional heat upgrades (mod-con boiler, outdoor reset, aquastats w/timers on domestic recirc lines, indoor setback thermostats with unoccupied settings). It is our intention not to simply scab on a solar array and green stamp a second home. We spend our time to do an overall system analysis and try to do our best to incorporate solar and modern efficient products. This normally results in us installing a DHW only system 90% of the time. However sometimes a client comes along and gives us some more rope. This is one of those situations.

As these homes are ridiculous in the sense of global warming, resource use etc. Shouldn't these people be the first to purchase higher priced, low market penetration new technologies? Thereby increasing the know how in the trades and lowering the price for the rest of the country?

It is my intention to try and design a good system, that integrates solar evac tubes with Mod-con boilers for use in new construction using low temp delivery. This project would not have been my first pick, however the owner is wealthy and understanding of its experimental nature. To do this I need to understand conventional hydronic at least as well as the solar. I am very appreciative of all the help and insight I gotten here.

Thermomax are designed and built here in the States, they are marketed under several names, including Viesmann (they use there own header)www.thermomax.com.
Trevor

hot_rod

Did you see Daves' Sungalow in Solar Today mag?

www.solartoday.org/2008/jan_feb08/sungalow.htm

This is the concept more builders need to look at. Gray water, solar DHW and heating, solar PV tiles. Near net zero energy in a 1500 square foot home.

Exactly what I would like my next home to look like.

hot rod

scott markle_2

Metro Man

Drain-back

Once you've seen a drain-back system (correctly installed) working you'll never go back. Get a hold of me if you like.... we fab our own stainless steel storage tanks for our customers... Don't really care much for bladder tanks. But whatever floats your boat and your comfortable installing.

Have MANY drain-back systems above 8000'.... not a problem.

And BO... yea I'm hoping to be knee deep soon.. if I can ever get out of here.

Metro Man

ALH_4

SDHW

I could not agree more. Domestic water heating has all the qualities that make it a good candidate for solar energy.

1. The DHW load is relatively consistent throughout the year.

2. The DHW load is diurnal.

3. The DHW load is low temperature.

4. A SDHW system is relatively simple, typically requiring one or two panels, a differential control, a circulator, and a pre-heat tank.

Swimming pools are probably even better, but not everyone has a pool. Our national energy policy should be leading us toward the installation of a SDHW system on every home in America.

Metro Man

DHW- not so low

If we are talking about a solar thermal to radiant heat solar usable temps may be btw 80 - 125*... usually lower end if good mass. Convertors & fan coils 95 & up.

DHW - 125 - 140* . 140 is now code I believe. So SDHW system although lower volume than rest of system is higher temps.

My 2c

Metro Man

ALH_4

Temps

The nice part about SDHW is that when the pre-heat tank is completely cold, it may be 50-60°F. Even if insolation is relatively low that day, the panels can work on that cold load at high efficiency. Also, if the pre-heat tank is completely discharged and recharged each day, the average temp would be lower than a radiant floor. A space heating storage tank can never be pulled down to the same temp as a sdhw pre-heat tank can be, and both have similar high limits. For that reason, I believe a SDHW system has a lower average temperature than a space heating system.

scott markle_2

Thermomax

Trevor, You make a good case. I'm only making noise to help bring out the issues you raise. Thanks for your reply. You are lucky to have patrons like this.

As far as the Thermomax tubes: Made in Ireland. I'm pretty sure there is no such thing as a U.S made evac. tube. Can you believe G.E made tubes?

By the way How are those Chinese tubes holding up, What sort of failure rates are you seeing? I'm interested in the non heat pipe design, But the ability to replace a bad tube without draining the header is a big advantage to the heat-pipe design.

As far as how to most efficiently integrate solar heating with a mod-con I think this is a challenging question. In my opinion just optimizing the performance of a mod-con on it's own is subject to a lot of design variables. One of the things I loth about high end multi-temperature systems is that much of the potential benefit of low temperature operation is lost to mixing or injection. We run the boiler for the high temp zones and mix down for the low temp and in most cases do not extract as much of the latent heat as possible because of this. Then we have short cycle issues, Yes we can heat with incredibly low(high condensing) temperatures when loads are low, but how does a control cope with this when turndown ratios are not great enough to cover these low load conditions, Short cycle....

So we add a buffer tank, But how efficient is it to have those added standby losses, Oh sure the tank is in the building envelope, but how much does the occupied space really benefit from mechanical rooms or basements that are warmed by this loss?

Add to these questions how to efficiently integrate solar and the task is even more complicated. I think a lot of mod-con instals already fall sort of their potential, Adding solar is no walk in the park.

Metro Man

big tanks

When we are talking about large solar systems 300 gallon+(one tank heating sdhw and space) the idle storage temps very rarely drop below room temp for residential applications. Commercial may be a bit different. You would have to run a lot of domestic hot water to cool a 1000 gallon solar storage tank to 60*F. But I agree the colder the water the higher efficiency the system will run. But I also think that using as many BTU's out of the solar storage tank for whatever loads building using is what it's all about.

Figure the sdhw loads per day and compare it to the total load of the solar system and sdhw will be a small percentage.

300 -400 sq ft of collector area as being discussed here puts this system as heating system 1st and domestic hot water 2nd. Therefore, utilizing as much of the cooler (85 - 100*) temps from the solar storage is critical when talking about overall efficiency of system(s)

Metro Man

ALH_4

Smaller

I'm sorry, I was talking about a completely different system. I was thinking more of an 80 or 120 gallon indirect tank with one or two collectors for a typical household. With laundry, showers, dishes, etc, the pre-heat tank could very easily be drawn down colder than a space heating storage tank ever would be. If the system is being used for space heating also, the situation would be very different.

The point I was attempting to agree with Scott about, is that a simple SDHW system utilizes solar energy better than a solar space heating system can.

Metro Man

Gotcha.. but

As homes get tighter and smaller and the radiant heating systems more efficient, offsetting the major load (heating in my neck of the woods) with a solar thermal system becomes very attractive. I just love watching solar heat a home with a 85* temps as the boiler sits idle

There is a big push to create zero energy homes (as in usage) using a solar thermal heating system to accomplish this is a very good way to go.

Good to see more and more contractors get on board.


Metro Man

Ed_26

US Mfg.

EOS solar - Nate chimed in on another thread earlier; 'bubble foil bubble' or something? Made in N.E. states?

scott markle_2

85 deg.

What I'm saying is that if you have wintertime 85 deg.water to spare (at a meaningful flow rate) and your DHW is satisfied this means you must have a lot of overcapacity in the summer, Or a very winter optimized (inefficient) collector angle.

While it's certainly very alluring to imagine an idle boiler, given the costs of these collectors and the environmental impact of their manufacture we should ideally instal them in a fashion that achieves the highest possible annual solar utilization. I have yet to see a convincing explanation of how this can be achieved in a heating application.

In northern latitudes even achieving 100% solar dhw is dogged by this. I believe the most efficient solar thermal dhw system is one that accomplishes no more than 100% of capacity in the summer, unfortunately this may only deliver 60-65% of total annual load. In my opinion this is the low lying fruit, of the alternative field, an obvious and indisputable energy source that could if widely adopted have a real impact on our energy security and CO2 emissions. Often less is more... to bad it can be so hard to market or profit from this truth. Sorry for repeating my self

scott markle_2

Implied US manufacture

I appreciated Nate chiming in on the last solar discussion. But I was unimpressed by his companies web site. I'm fairly sure these are Chinese tubes. I was put off by the implication that this is a US product and by the lack of substantive product documentation. Active heating was also mentioned as an application on this site, I say false promise, get real. Kudos to Viessmann a no nonsense company that provides the information required to make intelligent decisions about the best applications for their solar products. While they do provide schematics for supplemental heating systems they are very realistic about the limitations.

Ed_26

EOS

I have e-mailed for more info - yet to receive a reply. @ this point (planning) I am leaning sharply to FP for dhw. Time & more research will tell.

Metro Man

Well.....

If your off setting 50% of a your thermal load for the winter that can be a sizable load. Many systems come off higher than that. Amortize that in the home loan and it's not a tough pill to swallow. These also are loads that where driven (in newer construction) by high efficient heating systems. And depending upon what you are paying for gas or electric could be VERY significant.

We typically see 70 - 80% svgs off of ANNUAL loads. And yes lots of extra heat in the summer. Maybe I'll get into the pool business to dump heat.

Colorado in my opinion is a perfect state for this industry... we have the sun and the loads. Learning how to squeeze every bit of energy from your system is the trick. That is why I am so adamant on drain-back water systems. They're efficiency is very high but component list is very low. The more systems are purchased the more production will come and then hopefully lower prices to the end user. If gas goes to $5.00 / gallon (not likely in an election year - 09 is going to suck) things will change a bit.

Metro Man

hot_rod

\"no need to call a solar professional\"

they state at the EOS site. Easily installed by your own plumber. that seems like an odd way to promote. I wonder how many plumbers do the solar calcs and design work for a solar application.

If I were selling solar products I sure wouldn't want to distance myself from the solar professional. After all isn't that what they (EOS) promote themselves to be?

hot rod

NRTDave

Chinese tubes.

Scott,
They seem to be holding up quite well once they are installed, probably something in the order of 1 or 2% failure out of the box or during install. We should do a better job of tracking failure, and determining cause.

The truth is I spend more time tweaking big hydronic systems to improve efficiency than I do installing solar. These things can be as simple as large, mult-temp systems with 5-600 ft of large diameter pipe moving heat to the zones, all uninsulated in unconditioned crawl spaces. I found one that also had a radon mitigation, we were spewing out 30,000btus an hour when the temp was cold. Combative systems trying the heat and humidify an empty house. So I teamed up with a local solar installer, we are trying to tie the two ideas together. Most of the time, we just throw in a prefeed tank and only address DHW. However we find that the cost is not really in the material ie collectors, its in the labor of piping to the roof and setting, pumps, controllers etc. So why not try for a little heat.

I think if I can get a system that can adequately turn down when unoccupied, I might be able to idle a vacant house on solar (interior temp can dip to 45 or 50). This is obviously chancy and needs thorough thought before attempting. Any thoughts on communicating thermostats?
Trevor

Steve_174

Solar Heating

This is a big subject. Our company does this full time, both residential and commercial, and I see these questions often. We are thinking of doing training seminars for this purpose, because of the many pitfalls. What specific questions do you have?

hot_rod

Steve, call me

I'd like to chat when you have time, or e mail. 417 753-3998.

hot rod